Please advise on 12 hp i/c briggs
My daughter's lawn mower quit. She thinks that her Alzheimer's husband poured diesel in it. When I went to check it, it was low on oil, will still fire, seems low on compression, sucks pretty hard when cranked with finger over plug hole, but does not blow very hard. I could get it to hit a few times and try to run, but blows a lot of mist and a little smoke out the carb. At this time we don't have a lot of money to spend on repair. I am hoping to tear into it and check for damage, hoping for a burnt valve or maybe a compression release problem, but because of the low oil I fear something worse.
The engine is an older flat head design.
Thank you in advance, I know this is not a lot of info, but it is all I have at this time.
P.S. it is on a zero turn with joy stick controls if that makes any difference.